When starting a new venture, the only thing that is certain is it will not look like the thing you imagined at the seed of the idea. We start out putting something out there, we learn lessons, adjust, and try again. We keep running this sequence until we get something that works.
The really really really big question is, how long can you keep learning and adjusting (pivoting) before running out of money. The cheaper and faster your tests, the longer you can keep trying until the puzzle pieces fit together.
A former mentor used to tell me "cash is like gas." When the tank hits empty, everything stops.